Quality warranty system in induction heat treatment facilities

ABSTRACT

To provide a quality warranty system in the induction heat treatment facilities, in which the reliability of quality warranty can be increased because of the clarity of the processing conditions in each of the products which have been heat treated, and in which selection and identification of defective products once they occur can be facilitated. In the induction heat treatment facilities ( 1 ), there are provided a monitoring apparatus ( 3 ) for monitoring processing conditions in the induction heat treatment facilities ( 1 ) during the heat treatment of each of the products (W), and a recording apparatus ( 4 ) for recording information on the processing conditions, monitored by the monitoring apparatus ( 3 ), against an identification code of each of the products (W).

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation Application of International Application PCT/JP2007/000299 filed Mar. 26, 2007, which claims the benefit of priority Japanese Application No. 2006-086053 filed Mar. 27, 2006, the disclosures of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates to a quality warranty system for controlling a heat treatment quality for use in induction heat treatment facilities, in which metallic products, which will become component parts such as, for example, bearing parts, constant velocity universal joint parts, various shafts or engine parts, are heated through the induction heat treatment.

In the induction heat treatment, hardening or tempering is carried out by means of an induction heating. During the inspection of the quality of heat treatment, the surface hardness and the depth of an effective hardened layer are required to be checked, but those items are required to be checked with the use of a hardness testing machine and, therefore, products so inspected can no longer be used. Accordingly, it has been a general practice that the quality inspection is based on a sampling inspection, and, provided that products being monitored fall within the range of uppermost and lowermost values, which have been set up, as shown in FIG. 3, as a result of measurement of processing conditions conducted during the production, those products are deemed to be acceptable.

Also, for the inspection of the effective hardened layer, a non-destructive inspection using an eddy current is available, in which the use is made of a probe 51, as shown in FIG. 4A, to measure a product W. However, with this non-destructive inspection, the product W cannot be measured except for a localized portion thereof and, accordingly, the application of the non-destructive inspection using the eddy current is limited particularly where the product W has a plurality of locations to be inspected as shown in FIG. 4B.

It is to be noted that the following Patent Documents 1 and 2 discloses monitoring the state of heat treatment.

[Patent Document 1]

Japanese Laid-open Patent Publication No. 2001-226712

[Patent Document 2]

Japanese Laid-open Patent Publication No. 2001-294937

Since the quality inspection of the products which have been heated through the induction heat treatment is generally based on a sampling inspection, there is the possibility, as can readily be understood from FIG. 3, that some of the products not sampled for inspection may contain defective products that are caught up in and packaged for marketing together with those non-sampled products. Also, as shown in FIG. 5, once a defective product has been found during the sampling quality inspection, it is not possible to find where the defective product appeared and discrimination is not easy within one and the same lot, requiring all of the products to be discarded. In addition, even though the details of defectiveness could be identified, it is not easy to ascertain the cause (change in facilities or processing conditions) of such defectiveness.

SUMMARY OF THE INVENTION

In view of the foregoing, the present invention is intended to provide a quality warranty system utilizable in induction heat treatment facilities, in which the reliability of quality warranty can be increased because of the clarity of the processing conditions and the depth of the hardened layer in each of the products which have been heat treated, and in which selection and identification of defective products once they occur can be facilitated.

The quality warranty system in induction heat treatment facilities, in which heat treatment of metallic products are carried out by induction heating them by means of a heating coil, connected with a radio frequency power source, and cooling them with a cooling apparatus, according to the present invention includes a monitoring apparatus for monitoring processing conditions in the induction heat treatment facilities during the heat treatment of each of the products, and a recording apparatus for recording information on the processing conditions, monitored by the monitoring apparatus, against an identification code of each of the products.

In a preferred embodiment of the present invention, the quality warranty system may also include a hardened layer inspecting apparatus for inspecting on a non-destructive basis the depth of a hardened layer formed in each of the products as a result of the heat treatment. In this case, the recording apparatus records information on the depth of the hardened layer, inspected by the hardened layer inspecting apparatus, and the information on the processing conditions, monitored by the monitoring apparatus, against the identification code of each of the products.

According to the foregoing construction, when the identification code, applied by a marking apparatus to the products, is checked against the contents recorded by the recording apparatus, at least the processing conditions out of the processing conditions of the products and the depth of the hardened layer thereof can be ascertained. In such case, since at least the processing conditions is recorded for each of the products, the reliability of quality can be increased. Also, since the processing record corresponds to each of the products, selection of defective products when the latter occur and identification of a cause of defectiveness can be accomplished.

The hardened layer inspecting apparatus referred to above may be of any type, provided that the depth of the hardened layer can be inspected on a non-destructive basis, and can be employed in the form of, for example, a hardened layer inspecting apparatus of an eddy current type. Other than it, a hardened layer inspecting apparatus of an ultrasonic type can also be employed.

Also, the use of the marking apparatus for applying a marking of the identification code to each of the products is preferred.

BRIEF DESCRIPTION OF THE DRAWINGS

In any event, the present invention will become more clearly understood from the following description of preferred embodiments thereof, when taken in conjunction with the accompanying drawings. However, the embodiments and the drawings are given only for the purpose of illustration and explanation, and are not to be taken as limiting the scope of the present invention in any way whatsoever, which scope is to be determined by the appended claims. In the accompanying drawings, like reference numerals are used to denote like parts throughout the several views, and:

FIG. 1 is an explanatory diagram showing a conceptual construction of a quality warranty system in induction heat treatment facilities according to a preferred embodiment of the present invention;

FIG. 2A is an explanatory diagram showing the manner of control in the quality warranty system according to the embodiment of the present invention;

FIG. 2B is an explanatory diagram showing the conventional manner of control;

FIG. 3 is an explanatory diagram showing the relation between manufacture of products and processing condition according to the conventional control;

FIG. 4A is an explanatory diagram showing examples measurement performed with a hardened layer inspecting apparatus of an eddy current type;

FIG. 4B is another explanatory diagram showing examples measurement performed with a hardened layer inspecting apparatus of an eddy current type; and

FIG. 5 is an explanatory diagram showing the relation between the product manufacture and the quality according to the conventional control.

DESCRIPTION OF THE PREFERED EMBODIMENTS

A preferred embodiment of the present invention will be described in detail with particular reference to FIGS. 1 and 2. A quality warranty system for use in induction heat treatment facilities is of a type, in which a monitoring apparatus 3, a recording apparatus 4 and a marking apparatus 5 and, optionally, a hardened layer inspecting apparatus 2 are provided for use in the induction heat treatment facilities 1 for heat treating products W.

The induction heat treatment facilities are where a heat treatment of metallic products W, including hardening thereof, is performed by induction heating them by means of a heating coil 7, connected with a radio frequency power source 6, and cooling them in a cooling apparatus 8 and may be of a type capable of performing, for example, a tempering subsequent to the hardening or only a hardening. A heat treatment line is formed extending from the heating coil 7 to the cooling apparatus 8 and then to the hardened layer inspecting apparatus 2 and the marking apparatus 5 by a transport apparatus 12 for transporting the products W. The transport apparatus 12 is made up of a plurality of conveyors and/or loading apparatuses. The hardened layer inspecting apparatus 2 and the marking apparatus 5 may not be arranged in the order specified above. Also, the hardened layer inspecting apparatus 2 is not always essential and may therefore be dispensed with.

The products W may be any product, provided that they can be heat treated by means of an induction heating and may be mechanical component parts such as, for example, bearing parts (bearing rings and so on), constant velocity universal joint parts (joint members and so on), connecting rods, various shafts or engine parts.

The products W are supported by device 10, for example, a support table relative to the heating coil 7. In the instance as shown, the support device 10 is of a type that is driven by a motor 11 to rotate the products W within the heating coil 7. The products W may be heated by the heating coil 7 either all at a time or one at a time. The heating coil 7 may be of a type capable of induction heating the products W while the latter are relatively moved in a direction, for example, axially of each product.

The cooling apparatus 8 is an apparatus in which the products W, which have been heat treated, are cooled for hardening and includes a nozzle 8 a for discharging a coolant such as, for example, a cooling liquid onto the products W, a coolant supply source 8 b from which the coolant is supplied to the nozzle 8 a. This cooling apparatus 8 may be of a type capable of cooling the products W while the latter are immersed in a bath of a cooling liquid.

A production control apparatus 20 is an apparatus for controlling the induction heat treatment facilities 1 in their entirety and controls, for example, the recording apparatus 4 and the marking apparatus 5.

The monitoring apparatus 3 is an apparatus for monitoring the state of heating in the induction heat treatment facilities 1 during the heat treatment of the individual products W. Items of the heating state to be monitored by the monitoring apparatus 3 arc properly determined in dependence on, for example, the type of the products W and/or the heat treatment method used. Those items of the heating state to be monitored include at least one of the followings (a) to (c):

a) The electric power to be supplied from the radio frequency power source 6 to the heating coil 7 and/or the frequency of the radio frequency power source 6;

b) The position and/or the number of revolutions of the products W being heated relative to the heating coil 7; and

c) The flow and/or the temperature of a hardening cooling liquid in the cooling apparatus 8.

Monitoring of those items is carried out by monitoring respective outputs generated from detectors provided in the radio frequency power source 6 and the cooling apparatus 8.

The hardened layer inspecting apparatus 2 is an apparatus for measuring, on a non-destructive basis, the depth of a hardened layer Wa formed as a result of heat treatment of the individual products W and is employed in the form of, for example, an eddy current type hardened layer inspecting apparatus. The hardened layer inspecting apparatus 2 may be an ultrasonic type hardened layer inspecting apparatus. The hardened layer inspecting apparatus 2 employed in the illustrated embodiment is in the form of the eddy current type and includes probes 2 a, which can be neared to the products W, and a data processing unit 2 b for processing detection signals from the probes 2 a to provide a value of the depth of the hardened layer.

The hardened layer inspecting apparatus 2 is chosen to be of a type operable to measure the depth of a portion of the hardened layer Wa of the products W, which forms a representative portion thereof. The site of measurement may lie either at one location or a plurality of locations and, where the site of measurement includes a plurality of locations, the measurement may be made with the use of a plurality of probes 2 a one for each location or, alternatively, the measurement may be made by successively shifting the single probe 2 a from one location to another.

The recording apparatus 4 is an apparatus for recording information, which is related with the processing conditions such as, for example, an electric power supplied to the heating coil 7 monitored by the monitoring apparatus 3, and, optionally, information, which is related with the depth of the hardened layer inspected by the hardened layer inspecting apparatus 2, in correspondence with the identification code of the individual products W. The recording apparatus 4 may record, other than the information related with the processing conditions, information related with settings of various parts of the induction heat treatment facilities 1 such as, for example, information related with settings of the electric power of the radio frequency power source 6 to be supplied to the heating coil 7 and the frequency thereof, in correspondence with the identification code of the products W. The information related with the settings is controlled by the production control apparatus 20 and are then transferred to the recording apparatus 4.

The recording apparatus 4 is a so-called database and includes a storage unit 4 a for storing the previously discussed identification codes, the processing conditions and the information related with the depth of the hardened layer and a stored information control unit 4 b which is a database management system for processing inputs to and outputs from the storage unit 4 a.

The recording apparatus 4 may be the one provided in the same computer as the production control apparatus 20, in which case the use of the production control apparatus 20 may be dispensed with. Also, the recording apparatus 4 may be provided in a computer separate from the production control apparatus 20 and may be connected therewith through a network.

The marking apparatus 5 is an apparatus for applying a marking M, which forms the identification code that is recorded by the recording apparatus 4, to a corresponding product W and may be of a type capable of, for example, imprinting the marking M. This marking apparatus 5 may be of any type, provided that it can apply the identification code to the product W, and can be employed in the form of an apparatus capable of applying the identification code in any one of various methods other than imprinting. The marking apparatus 5 may be of a type capable of applying to the product the identification code in the form of, for example, a code such as, for example, a bar codes, or an IC tag. In this marking apparatus 5, the identification code is acquired from, for example, the production control apparatus 20, but may acquire from the recording apparatus 4 rather than from the production control apparatus 20.

The operation of the above described construction will now be described. The products W are heat treated by the heating coil 7 excited by the radio frequency power source 6 and are then hardened when cooled by the cooling apparatus 8.

During this heat treatment, the processing conditions, which are represented by the electric power of the radio frequency power source 6 to be supplied to the heating coil 7 and the frequency thereof, are monitored by the monitoring apparatus 3 and values so monitored are recorded in the recorded apparatus 4 each time the individual products are heat treated. The identification codes corresponding to the recording are applied to the products W and, in the recording apparatus 4, the above described processing information is recorded in correspondence with the identification codes.

The depth of the representative portion of each of the products W, which have been heat treated, may be measured on a non-destructive basis by the hardened layer inspecting apparatus 2 of the eddy current type. The depth of the hardened layer so measured is ascertained by a determining module (not shown) that it falls within a required depth range (that is, a preset range of depth) and is recorded by the recording apparatus 4 together with the processing information in correspondence with the identification information.

FIG. 2A illustrates a concept of control of the heat treatment applied to the products W according to this embodiment of the present invention and FIG. 2B illustrates a concept of the conventional control.

As can readily be understood from those figures, in the quality warranty system according to the foregoing embodiment, for each of the products W the processing information and, optionally, the depth of the hardened layer are recorded together with the product identification information. Because of this, the reliability of quality increases. Also, since for each of the products W, the product and the processing record are associated with each other, selection of defective products, when the latter occur, and identification of a cause of defectiveness can be accomplished.

It is to be noted that the marking apparatus 5 can be dispensed with, in which case the identification code applied beforehand to the corresponding product is read out by the monitoring apparatus 3 or the production control apparatus 20. 

1. A quality warranty system in induction heat treatment facilities, in which heat treatment of metallic products are carried out by induction heating them by means of a heating coil, connected with a radio frequency power source, and cooling them with a cooling apparatus, which system comprises: a monitoring apparatus for monitoring processing conditions in the induction heat treatment facilities during heat treatment of each of the products; and a recording apparatus for recording information on the processing conditions, monitored by the monitoring apparatus, against an identification code of each of the products.
 2. The quality warranty system in induction heat treatment facilities as claimed in claim 1, further comprising a hardened layer inspecting apparatus for inspecting on a non-destructive basis the depth of a hardened layer formed in each of the products as a result of the heat treatment and wherein the recording apparatus records information on the depth of a hardened layer, inspected by the hardened layer inspecting apparatus, and information on the processing conditions, monitored by the monitoring apparatus, against the identification code of each of the products.
 3. The quality warranty system in induction heat treatment facilities as claimed in claim 2, wherein the hardened layer inspecting apparatus is a hardened layer inspecting apparatus of an eddy current type.
 4. The quality warranty system in induction heat treatment facilities as claimed in claim 1, further comprising a marking apparatus for applying a marking of the identification code to each of the products.
 5. The quality warranty system in induction heat treatment facilities as claimed in claim 1, wherein the monitoring apparatus monitors at least one of the following items (a) to (c): a) an electric power to be supplied from a radio frequency power source 6 to a heating coil 7 and/or the frequency of the radio frequency power source 6; b) the position and/or the number of revolutions of the products W being heated relative to the heating coil 7; and c) the flow and/or the temperature of a hardening cooling liquid in the cooling apparatus
 8. 